Selective reactive ion etching of polysilicon against SiO.sub.2 utilizing SF.sub.6 -Cl.sub.2 -inert gas etchant

Abstract

Disclosed is an improved Reactive Ion Etch (RIE) technique for etching polysilicon or single crystal silicon as must be done in Very Large Scale Integration (VLSI) using silicon technology. It teaches the use of an etch gas that consists of a mixture of sulfur hexafluoride (SF.sub.6) and chlorine (Cl.sub.2) diluted with inert gas. This etch gas allows an RIE process which combines the very desirable features of selectivity (high Si/SiO.sub.2 etch rate ratio) and directionality which creates vertical side walls on the etched features. Vertical side walls mean no mask undercutting, hence zero etch bias. It is particularly applicable to device processing in which micron or sub-micron sized lines must be fabricated to extremely close tolerances. It is a distinct improvement over wet chemical etching or plasma etching as it is conventionally applied.

Dependencies are inferred from the claim text.